(1) Field of the Invention
This invention relates to a color separation system which is capable of systematically controlling various picture input and output units, such as color scanners, used in a process for making printing plates.
(2) Decription of the Prior Art
A photographic plate-making process requires a color separation system for color-separating an original picture to be printed so that printing colors are determined. A color scanner, which converts picture signals to four-color proof signals suitable for reproduction by printing techniques, provides printing plates corresponding to the printing inks of the four colors, namely the yellow(Y), magenta(m), cyan(C) and black(K) inks, or photographic films suitable for use in the fabrication of such printing plates.
Such color scanners may be roughly classified into the following groups, depending or their functions and peripheral equipments:
(1) so-called monofunctional scanners, each of which is adapted to set up, color-separate and print directly on a photographic film or the like, originals one by one;
(2) so-called layout scanners, each of which is adapted to store data for a color-separated picture in a mass storage such as disc memory or the like and then to control the thus-stored data suitably by means of a computer, thereby printing the thus-stored data together with picture data, which are separately supplied and may include other picture signals, characters and the like, on a photographic film of the like in accordance with a designated layout; and
(3) setting-up units, each of which is adapted to simulate beforehand color separation conditions in a desired output state (in a printed form) so as to establish the setting-up conditions of a color scanner by means of a color monitor.
However, units such as these monofunctional color scanner, layout scanner, original setting-up unit and the like have heretofore been used as independent units in a photographic plate-making process and their functions have not thus been shared by one another. Hence, the efficiency of their use has been poor. This inefficiency can be attributed to the fact that the picture input systems in the monofunctional color scanner, original setting-up unit, layout scanner and the like handle multi-colored picture signals respectively by methods which are different from one another and the arithmetic processing unit and picture reproducing unit cannot thus be designed systematically.
Moreover, conventional arithmetic processing units are primarily constructed of analog circuits. Their setting-up operations are carried out by operating, for example, their potentiometers or rotary switches. Therefore, their use efficiencies are low and their standardization with the picture input unit and picture reproducing unit have encountered difficulties.